The present invention relates in general to motor cars with four-wheel steering.
More particularly, the invention concerns a mechanical steering device for the rear wheels of cars with four-wheel steering, including a front steering unit and a rear steering unit coupled for rotation with each other by means of a longitudinal transmission shaft, and in which the rear steering unit comprises a transverse bar connected to the rear wheels by means of respective steering joints and tie rods, and transmission means for transforming the rotation of the longitudinal shaft into translation of the transverse bar.
Mechanical steering devices of this type are known, for example, from U.S.-A- U.S. Pat. No. 4,557,493 and U.S.-A- U.S. Pat. No. 4,522,417. In these known devices, the transmission between the longitudinal shaft and the transverse bar includes a cascade connection of eccentric shafts using a movable crown wheel in contact with a fixed ring gear. This type of transmission enables reversal of the orientation of the rear wheels which are steered in phase with the front wheels for limited angles of rotation of the steering wheel and in counterphase with front wheels at large angles of rotation of the steering wheel. The disadvantage of these known devices lies on the one hand in a considerable structural complexity, and on the other hand in the practical impossibility of achieving steering laws other than pseudosinusoidal laws.